Two stories of neglected history have won this year's Commonwealth writers' prizes. African-Canadian novelist Lawrence Hill has won the headline prize for his novel The Book of Negroes, based on the true story of a Malian woman's journey from enslavement in Africa to bondage in South Carolina and finally back to Africa. The parallel prize for a first novel was presented to Tahmima Anam for A Golden Age - previously shortlisted for the Guardian first book award - for her story of the Bangladesh war, A Golden Age.

Speaking from Cape Town after receiving his £10,000 award at a ceremony at the Fransschoek literary festival, a delighted Hill said his story related to a virtually unknown chapter of history. "It's particularly good to receive the prize in South Africa," he added, "because its history mirrors my protagonist's journey from oppression to liberation".

The Book of Negroes is not yet published in the UK, but it has appeared in the US under the title Someone Knows My Name - according to Hill, the title was changed "because the publishers thought 'negro' was an incendiary term".

A contentious title is not the only obstacle he has found in reaching an international audience. "My publisher told me that there was an acute, additional challenge for African-Canadian writers trying to get published in the UK," he explains. "If a book is thematically black, publishers there will look to the US. It is apparently not thought to be as fully authentic as American work, though the history is just as thematically complex."

In Hill's own case, the example of a previous Commonwealth prize winner augurs well. The only other African-Canadian novel to have won the prize, Austin Clarke's The Polished Hoe, is also the only such novel published currently in the UK.

Tahmima Anam's A Golden Age follows the impact on one family of the 1971 war for Bangladeshi independence. Anam, who received a cheque for £5,000, said she was "honoured and humbled to be the first ever Bangladeshi winner.

"I wrote A Golden Age because I wanted the story of the war to reach an international audience. It is a story of great tragedy, but also represents a moment of hope and possibility for my sometimes troubled country."

In receiving the best book prize, Lawrence Hill has also been invited to an audience with the Queen at Buckingham Palace. The 2004 winners Caryl Phillips and Mark Haddon caused some controversy when they refused to meet her because of misgivings about the institution of the monarchy, but Hill declared himself unworried by the political implications of an audience with the head of the Commonwealth.

"I think it should be fun," he said, "particularly because my leading character also meets the British monarch in England to appeal for the end of slavery."

The Commonwealth Writers' Prize was established in 1987, and its previous winners include Rohinton Mistry, Peter Carey and JM Coetzee. Last year's winner was Lloyd Jones's Mister Pip, which went on to be shortlisted for the Booker prize. To be eligible, the authors must be citizens of one of the Commonwealth's 53 member countries and write in English. Each year there are separate regional shortlists, and prizes of 1,000 before all of the winners are considered. The winners were chosen by a panel of judges from six different countries who met over two days during the final programme.

Canada and Caribbean Best Book: Lawrence Hill (Canada) The Book of Negroes HarperCollins Publishers Best First Book: C S Richardson (Canada) The End of the Alphabet Doubleday Canada

Europe and South AsiaBest Book: Indra Sinha (India) Animal's People (Simon and Schuster)Best First Book: Tahmima Anam (Bangladesh) A Golden Age (John Murray)

South East Asia and South PacificBest Book: Steven Carroll (Australia) The Time We Have Taken (HarperCollins)Best First Book: Karen Foxlee (Australia) The Anatomy of Wings (University of Queensland Press)